The present invention relates to an image information reading system and more particularly to an image information reading system for performing read scanning of image information and reproducing the same appropriately in accordance with a selected scanning line density in facsimile apparatus or the like.
In a conventional image information reading system, main scanning is performed electronically by using a reading head in which self-scanning type light receiving elements are arranged in the main scanning direction for scanning one line, while subscanning is performed by moving the original document mechanically using a motor, whereby the read scanning of image information is carried out.
Therefore, in the conventional image information reading system, the original document has to be moved intermittently line by line or several lines at a time when performing the subscanning. This makes it difficult to sustain a stable reading operation.
More specifically, when the motor for subscanning is driven intermittently, the space between each read scanning line varies due to the inertia of the motor when it is started or stopped, so that main scanning is not always performed in a parallel manner and therefore image information is not reproduced appropriately.
The applicants of the present invention have proposed an inexpensive facsimile apparatus capable of performing the read and record scanning, with the above-mentioned conventional shortcomings eliminated, in U.S. patent application Ser. No. 967,834 filed Dec. 18, 1978, now abandoned and German patent application O.S.L. 2,854,845 filed Dec. 19, 1978.
Generally, in facsimile apparatus, in order to increase information transmission efficiency when image information is transmitted from a sending side to a receiving side, it is necessary to select a suitable scanning line density for each original document, depending upon the kind and quality of the image of each original document.
If the scanning line density is low, the image information between each read scanning line may be omitted and accurate image information may not be transmitted to the receiving side.
In order to eliminate such omissions of image information, it is necessary to perform the read scanning of image information with a high read scanning line density all the time, or, if the read scanning line density is set low, the image information for a plurality of lines has to be subjected to a logic processing.
However, when the above-mentioned methods are utilized in conventional image information reading apparatus, a memory means is required for storing the image information for the plurality of line readings to be output from the reading head, so that the image information reading apparatus becomes expensive.